The Drosophila protein Dock is an adapter protein found in axonal growth cones that potentially provides a link between guidance cue receptors and changes in the cytoskeleton. dock null flies experience axonal projection defects in four defined systems. Dock associates with p145 in Drosophila embryos and Schneider 2 cells. Protein sequence generated from purified p145 indicates that it belongs to the family of Activated Cdc42hs tyrosine kinases. P145 will be fully cloned and its interaction with Dock will be characterized. Local P element hopping will be utilized to generate mutant p145 Drosophila. Multiple p145 alleles will be isolated and their guidance phenotypes will be compared to those seen in dock mutants to assess the role of p145 in axonal guidance.